The present invention relates to a heated roller of the type in which the heated roller has a cylindrical roller body that rotates around its axis and has an outer cylindrical surface that serves as the roller working surface. The roller has a first inside cavity arrangement as well as a second cavity arrangement in the form of several elongated axis-parallel channels, separate from one another, that are evenly distributed over the circumference of the roller body and which are sealed at their ends.
Axis-parallel channels have long been known in connection with heating of rollers, e.g. from DE-GM (utility model) 90 14 117, where they don't form a closed system, however, but rather have a heat carrier fluid flowing through them which is heated and pumped in circulation outside the roller.
In German Patent 40 33 986 A1, no heating elements are arranged in a central bore of the roller body, and rod-shaped electrical heating elements are arranged in the peripheral channels, which are partially filled with a convection fluid capable of boiling.
Elongated axis-parallel channels can be produced in the roller body using known means, with relatively little effort, and leave the roller body essentially unimpaired in its stability. The term "elongated channels" in this contexts means that the cross-sectional area of the channel is not important and that the length of the channels is a multiple, e.g. 20 to 150 times, of the cross-sectional dimension. In practice, these are so-called peripheral bores made in the roller body close to its outside circumference. These bores contain the heating elements, the connections of which must be brought out at the ends. This requires complicated seals, because of the high pressures in the bores. Because of the closeness of the heating elements to the roller circumference, the temperature distribution in the circumference direction of the roller circumference is frequently uneven.